1. Field of the Invention
This invention relates to belt drive systems for vehicles and, more particularly, to a belt drive system for lawn and garden tractors, walk-behind mowers and other vehicles which utilize a constant engine drive speed to propel the vehicle at variable speeds.
2. Description of the Related Art
Variable speed transmission assemblies for lawn and garden tractors and self-propelled walk-behind mowers allow for the ground speed to be varied while maintaining a constant engine speed. Constant engine speed facilitates, for example, effective cutting by mower blades. Previous variable speed transmission designs, such as those disclosed in U.S. Pat. No. 6,142,898 (Miyata), have incorporated various planetary gear arrangements. Other variable speed transmission designs, such as those disclosed in U.S. Pat. No. 4,484,901 (Toti et al.) and U.S. Pat. No. 4,934,989 (Furukawa et al.), include multiple drive belt and multiple pulley systems to propel a mower or tractor while still maintaining a constant engine speed.
Planetary gear arrangements usually include a series of intermeshed gears to provide a suitable mower axle speed when the engine is operating at a relatively fast engine shaft speed. A problem with such planetary gear arrangements is that they considerably increase mower costs. Multiple drive belt and pulley systems, such as that disclosed in U.S. Pat. No. 4,934,989 (Furukawa et al.), typically include at least one belt tensioner or idle pulley which is merely used to maintain tension on the belts. However, these systems generally require more space and, like planetary gear arrangements, increase the mower costs since the systems require more expensive assembly operations.
An inexpensive infinitely variable speed transmission which includes a declutching mechanism and allows for greater ease of control by the operator would be highly desirable.
The present invention provides a variable speed transmission which overcomes the disadvantages of prior transmissions and/or speed controls therefor by providing an inexpensive variable speed transmission that requires less space through the use of self-adjusting pulleys. Additionally, a clutch mechanism is provided on the transmission for clutching and declutching the transmission. Furthermore, the operator need only move the pivot arm of the transmission to cause a change in the speed of the transmission, thereby providing ease of control of the transmission. The variable speed transmission may include an electronic speed control to prevent the varying the speed setting of the transmission while the engine is not running and to facilitate easy ground speed changes to an implement, such as a walk-behind mower, having the inventive transmission. Furthermore, the electronic speed control allows the operator to select the desired speed by tapping a switch, thereby providing additional eases of control of the transmission.
The present invention provides a variable speed transmission including a housing, a drive shaft having an axis of rotation and rotatably supported in the housing, an output shaft having an axis of rotation and rotatably supported in the housing, a first pulley and a second pulley both having a common axis of rotation, a third pulley having an axis of rotation and rotatably attached to the drive shaft, and a belt. The output shaft is operatively connected to the drive shaft. The first pulley and the second pulley each have a variable pitch diameter and changes in the first and second pulley variable pitch diameters being inversely proportional. The third pulley and one of the first and the second pulleys are in engagement though the belt.
The present invention further provides an implement including a deck, an engine attached to the deck and having a pulley, an axle rotatably supported by the deck, a ground engaging wheel driven by the axle, a variable speed transmission attached to the deck, and a drive belt. The variable speed transmission includes a housing, a drive shaft having an axis of rotation and rotatably supported in the housing, a first variable pitch diameter pulley and a second variable pitch diameter pulley having a common axis of rotation, a third pulley rotatably attached to the drive shaft, and a transmission belt. The drive shaft is operatively connected to the axle. The first variable pitch diameter pulley has a first variable pitch diameter and the second variable pitch diameter pulley has a second variable pitch diameter and the first and the second variable pitch diameters are in an inversely proportional relationship. The third pulley assembly and one of the first and the second variable pitch diameter pulleys are in engagement though the transmission belt. The drive belt extends between the engine pulley and the other of the first and second pulleys.
The present invention further provides an electronic ground speed regulator for an implement including a variable speed transmission having a speed control mechanism, an electric linear actuator in communication with the speed control mechanism, an electronic control circuit in electrical communication with the actuator, and an operator-manipulated switch in electrical communication with the electronic control circuit. The actuator has a first position and a second position and is moved therebetween in response to changes in an electrical input to the actuator, and the speed control mechanism is varied in response to movement of the actuator from one of the first and second positions to the other of the first and second positions. The electronic circuit has a first condition wherein the electronic control circuit maintains the actuator in one of its first and second positions and a second condition wherein the electronic control circuit controls movement of the actuator between its first and second positions. Movement of the actuator is controlled through manipulation of the switch.